Significant Accounting Policies, Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Accumulated other comprehensive income [Roll Forward]
Beginning balance				$ 257,780
Ending balance		$ 300,320		300,320
Unrealized (Losses) Gains on Investments [Member]
Accumulated other comprehensive income [Roll Forward]
Beginning balance		47,114	$ 29,000	39,747	$ 21,080
Other comprehensive income before reclassifications, net of tax	[1]	(28,703)	(4,456)	(21,336)	3,806
Amounts reclassified from accumulated other comprehensive income	[2]	0	175	0	(167)
Net current period other comprehensive (loss) income		(28,703)	(4,281)	(21,336)	3,639
Ending balance		18,411	24,719	18,411	24,719
Income tax expense (benefit) included in other comprehensive income		$ (5,100)	$ 2,900	$ 0	$ 2,500

[1] Other comprehensive loss for the three months ended June 30, 2015 includes income tax benefit of $5.1 million, compared to $2.9 million for the same period in 2014. For the six months ended June 30, 2014 other comprehensive income includes income tax expense of $2.5 million. There was no tax expense or benefit for the six months ended June 30, 2015.

[2] Included in gain on investments, net on our condensed consolidated statement of operations.